functional safety en iso 13849-1 (pl) · data from the application calculation according to norm...
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a
b
c
d
e MTTFd = low, MTTFd = medium, MTTFd = high
Category B DCavg =
0
1 DCavg =
0
2 DCavg =
low
2 DCavg =medium
3 DCavg =
low
3 DCavg =medium
4 DCavg =
high
Simplified graphic determination of the PL reached.Relationship between the categorie, DC, MTTFd and PL
Functional safetyEN ISO 13849-1 (PL)
Detecting
Sensor
Alerting
Logic Actor
Evaluating
Safety Instrumented System SIS (Safety Loop)
Machine safety, e.g. start-up warning
Command device
S2
Command device
S1
Start-up controlK1 (logic)
Safety contactor Q1 (actor)
Warning signal P1
Diagnosis unit G1 (sensor)
Machine control K2
PL bar chart according to ISO 13849-1
Risk assessment
Evaluation of the safety function
Calculation according to EN ISO 13849-1
Calculation is done with a source of:
Data from manufacturer
Data from the application
Calculation according to norm
Determination of the required Performance Level (PLr)
Risk parameters} S – Severity of the injury S1 = minor injuries (normally reversible) S2 = serious injuries, including death (normally irreversible)
} F – Frequency and/or length of exposure to the hazard F1 = rarely to more often and/or short periods F2 = frequently to continuously and/or long duration
} P – Possibilities to avoid danger P1 = possible under certain conditions P2 = barely possible
PL�
Value ranges
NameDiagnostic coverage
(DC)Average time until a
dangerous failure (MTTFd)
none DC > 60%
low 60% ≤ DC > 90% 3 years ≤ MTTFd > 10 years
medium 90% ≤ DC > 99% 10 years ≤ MTTFd > 30 years
high 99% ≤ DC 30 years ≤ MTTFd > 100 years
10-8
10-7
10-6
3 x 10-6
10-5
10-4
PFH[1/h]
Required safety related parameters
EN ISO 13849-1 Device typePLKategorieT1
-Units with internal diagnosis safety control
safety switch gears
MTTFd DC, CCF, category Units
without internal
diagnosis
Without omponents that are
subject to wear and tear
sensors, signaling devices
B10d DC, CCF, category, nop
With omponents that are
subject to wear and tear
emergency shutdown, relay, switch
CCF: failure due to common causeDC: diagnostic coverage
nop
MTTFd
MTTFd
Component 1Not subject to wear and tear;
without internal diagnosis MTTFd
Component 3Subject to wear and tear; without internal diagnosis
B10d
Component 2 With internal diagnosis
PL, KAT, PFH
➞
MTTFd
DC, CCF, KAT
PLPFH
&
PL, PFH➞
Minor risk
PerformanceLevel required
(PLr)
High risk
Starting point for risk
evaluation
PL/PFH [1/h] in comparison to SIL
PL PFH [1/h] SIL
a ≥ 10-5 ... > 10-4 = no equivalent
b ≥ 3 x 10-6 ... > 10-5
≙ SIL 1c ≥ 10-6 ... > 3 x 10-6
d ≥ 10-7 ... > 10-6 ≙ SIL 2
e ≥ 10-8 ... > 10-7 ≙ SIL 3
G1
K1
Q1
PL PL1≥Verification: ?